Blind fix for a Linux only crash in AudioManager::Destroy

media/audio/audio_manager.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/audio/audio_manager.h"
 
 #include "base/at_exit.h"
 #include "base/logging.h"
 
 static bool g_destroy_called = false;
 static AudioManager* g_audio_manager = NULL;
 
 // static
 void AudioManager::Destroy(void* not_used) {
   g_destroy_called = true;
 
-  g_audio_manager->Cleanup();
+  if (g_audio_manager) {
+    g_audio_manager->Cleanup();
 
-  AudioManager* audio_manager = g_audio_manager;
-  g_audio_manager = NULL;
-  delete audio_manager;
+    AudioManager* audio_manager = g_audio_manager;
+    g_audio_manager = NULL;
+    delete audio_manager;
+  }
 }
 
 // static
 AudioManager* AudioManager::GetAudioManager() {
   if (!g_audio_manager && !g_destroy_called) {
     g_audio_manager = CreateAudioManager();
     g_audio_manager->Init();
     base::AtExitManager::RegisterCallback(&AudioManager::Destroy, NULL);
   }
   return g_audio_manager;
 }